Interurban telephone system



July l, 1947 c. F. STEWART ET Al. 2,423,123 A INTER-URBAN TELEPHONE SYSTEM Filed Sept. 27, 17943 July l, 1947.

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INTER-URBAN TELEPHONE SYSTEM Filed sept. 27. 1945 sheets-sheet 2 July 1, 1947.

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INTER-URBAN TELEPHONE SYSTEM Filed sept. 27, 1945 7 Sheets-Sheet 5 INVENTORS July'l, 1947. c. F. STEWART ErAL 2,4?3J23 INTER-URBAN TELEPHONE SYS TEM Filed Sept-` 27. 1943 '7-Shees-Sheet 4 INVENTORS July 1, 1947. c. F. STEWART ETAL yI NZTER-URBAN TELEPHONE SYSTEM I T Sheets-Sheet 5 Filedsept. 27. 194;

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INTER-URBAN TELEPHONE SYSTEM 7 Sheets-Sheet 6 Filed Sept. 27. 1945 AGE July l, 1947 c. F. STEWART l-:r AL 2,423,123

l INTERURBANI TELEPHONE SYSTEM Filed sept. 27,- r1945 7 sheets-sheet 7 `atenteol July 1, 1942 INTERURBAN TELEPHONE SYSTEM Claudius F. Stewart and Gabriel J. M. Penet,

Paris, France, assignors to International Standard Electric Corporation, New York, N. Y., a

corporation of Delaware Application September 2.7, 1943, Serial No. 504,084 In France June 13, 1939 8 Claims. 1

The present invention relates to new and useful improvements in telephone systems comprising exchanges connected by inter-urban toll trunk lines in which calls between subscribers of different exchanges may be established by the operator at the outgoing central exchange, without the assistance of the operator at the incoming central exchange, the operator at the outgoing exchange being, nevertheless, able to call and communicate with the operator of the incoming exchange.

More particularly, the invention relates to systems in which the required instructions, or signals, are transmitted in the form of A. C. impulses of a single frequency. Known systems oi this type have the serious drawback that, for one reason or another, the normal impulse transmitting cycle between the exchanges gets out of order, and it may happen that the incoming equipments at the two exchanges are interconnected through an inter-urban toll circuit in such a way that their automatic release at the end of the conversation will be impossible.

In accordance with one of the features of the invention, this drawback is eliminated by making the switching and release impulses sent from the outgoing exchange long, while the return impulses sent from the call exchange short. The direction, or effect of the short and long impulses on a circuit, is fixed by the outgoing exchange and cannot be reversed, or changed, even if the transmission cycle is interfered with, unless the outgoing equipment of the said outgoing exchange has been released, that is to say, unless the incoming exchange has become the outgoing exchange after complete release of the first outgoing exchange. Thus, it is made impossible that input equipment in the two exchanges may become interconnected.

Other characteristics features of the invention will more fully appear from the description which will be given with reference to the attached drawings, which diagrammatically represent:

Fig. 1, an outgoing equipment used in conjunction with inter-urban switchboards in which the dialling key may cause switching in the circuit equipment;

Fig. 2, an input equipment in conjunction with the inter-urban boards, and an automatic switchboard;

Fig. 3, a re-transmitter recorder operating in conjunction with the input equipment;

Fig. 4, equipment comprising a group of operator calling relays designed to be introduced between the input equipment and the inter-urban switchboard;

Fig. 5, outgoing equip-ment used in conjunction with inter-urban switchboards in which the dialling key does not cause switching in the circuit equipment;

Fig. 6, input equipment for the exchange, not including an automatic switchboard; and

Fig. '7, the manner in which the different Figs. 1 to 6 should be connected.

In the description which follows the relay contacts which are closed when the relay is energized, that is to say, in operating position, are designated by'placing the letter T in front of the number oi the spring, and the contacts which are closed when the relay is not energized, that is to say, in non-operating position, by placing the letter Rin front of the number of the spring. The contacts of the make and break switches are shown on the figures by shaded squares provided with reference numerals designating the positions of the wipers, for which the make and break switch closes the contact and with reference letters identifying the wiper of the make and break switch which closes the contact.

First, with reference to Fig. 1, the detailed operation of the outgoing equipment will be described. This equipment is designed to be used in conjunction with the operators position in which the operator operates a key or button before and after dialling the number of the called subscriber, the call from the operator at the incoming exchange being established by operating a key or calling button.

It is assumed that the toll operator at exchange A (Fig. 7) wishes to call a subscriber in exchange B.

Normally, when the apparatus are disengaged, the relay 3 of the input equipment (Fig. 2) is energized in the circuit: battery, winding of 3, RAI, REI, RZI and earth. Relay 3 of the outgoing equipment (Fig. 1) is energized in the circuit: battery, wiper a of the make and break switch in position 0, wire C, T32, RSI, RZI and earth. At T32 (Fig. 1) the circuit of the disengaged lamp In is established.

By operating the lighting-up key L (Fig. 1), the operator A can make sure that the equipment is disengaged. She then plugs one of her cord circuits in Jthe calling jack J1. The following circuit for relay l (Fig. 1) is completed: battery, winding of the relay l, Rl53', TI3, body of the jack J1, and earth through the relays of the third or sleeve wire of the cord circuit which are not shown. At T12, the relay l establishes the circuit of relay I3 which insulates at RI32 and RI3I' the outgoing equipment of Fig. 1 from the incoming equipment in Fig. 2, and connects the said 3 outgoing equipment to the inter-urban circuit L1-L2.

Over TI2, the relay I closes through wiper C of the make and break switch in the position 0, the circuit of the stepping magnet Cmi of the make and break switch. The magnet C'mi attracts itsarmature, breaks its own circuit, and steps the wipers of the switch by one step into position 1.

The circuit of the relay 8 is closed by theA wiper a of the switch in the position 1. At Tl, the relay 8 establishes the circuitot thek upper winding of the relay 9 which, in T63, closestlie tol-- lowing circuit for the relay battery, non-inductive upper winding of the relay l', T93, lower winding of 'I and earth. The relay l'. closes its holding circuit at T12.

The alternating current of the generator G1 is transmitted over the inter-urban circuit Li-I'Lz through T92, TI32, conductor L1 and TSI', TISI conductor L2 to the receiving equipment of the exchange B.

When the make and break switch moves into position l, the circuit of the relay 3- is opened in the wiper a and this relay drops.

When the operator A depresses her-dialling'key battery is applied to the ring wire n of the jack JgI' and theY following circuit is closedv for relay 5: battery on the ring-nv of J'I', R124, series'windingsr of relay 5,y TII, wiper e of. the switch in position 1 and earth. The relay 5 locks up over T52' and through T5I` closes a circuit for the lower winding of the relay IB', which becomes energized.

The stepping circuit ofthe switch is closed: earth, interrupter Cai, wiper c in position 1, Tlgmagnet Cml and battery. The switch advances stepY by step. When the wipers have passed position 4, the circuit of the relay 8 throughy the wiper` a is opened, and this relay drops. At TSI, the relay 8 opens thek circuit of the upper winding1 of 9, which drops. At R93, the. relay 9- short-circuits. the lower inductive winding ot 1, which drops. When the relay 9 has dropped, conductors Li-Lz of the trunk line are disconnected from generator. Gi. and the transmission. of alternating current is terminated.

The durationY of the transmission from the moment when the operator depressesher dialling key, is determined by the time taken by the make and, break switch to advance from position 1 to position 5 under the control of interrupter Cai. A long impulse is thus transmittedv to the input equipment (such as that in Fig. 2)l of the called distant exchange B.

When the; make andY break switch reachesposi.- tion, the circuit offmagnet Cm; is closed through the wiper c in positions fto 10 tothe cam Cai. In positionr 11, the circuit of the magnet is closed tothe earth at RIE] and the wiper b of the make. and break. switch; For the positionsv 12 to 21, the circuit ofthe magnet isolosed to earth inRI2I via the wiperf oftheswitch.

These operations are repeated; thatisl to. say, theirelay isV energized, the relay S'isenergized'; and there is transmitted; over the toll; trunk circuit L1-L2- anA A. C. long impulse.y (for ex.- ample, 700A milliseconds). The.. transmission.. is stopped for a certain period (say one second), new long impulse, etc., until' a4 short impulse (10()A milliseconds, for example) is sent byA the inputA equipment of the distant exchange B, and isl received by the outgoing4 equipment, Fig. 1. This impulse is received by the relay 2Y through:

4 conductor L1, TI32, R92, RII3, relay 2, RIII, R9 I, TI 3 I conductor L2.

Through T2I, the relay 2 completes the circuit of the lower winding of the relay II which, by means of its springs III and II3, cuts ol the conductors Lie-L2 from the relay 2, and connects them to the relay 4. Relay 4 in this way receives the rest of the impulse emanating from the B exchange. The relay II whose new circuit is closed at Till, is held during this transfer, as it is retarded in release by its upper winding which is` short-circuited by TIM. The following circuit for therelay I5 is then closed: earth, T4I, RMI', RI5I", lower winding of the relay l5 and battery.

When the impulse has been received, the relay 4- drops, The relay I5 is held over the lower winding of I5', TI52, TI2 and earth. The relay I5 is energized. The following circuit for relay I2 is then established: earth, upper winding of I2, TI54, non-inductive lower Winding of` I2 and battery. The relay I 2 is. held and closes its holding circuit at TI22.

At RI.5I, the stepping circuit of the make and break switchis open in position 11, and the switch stops in this. position.

The non-inductive lowerA winding of the relay i isA nov longer short-circuited in RI53v which causes the lamp of the cord circuit plugged in at J I to light up. The. operator is thus advised and perceives the signal transmitted by the distant exchange. She then proceeds to dial the called subscribers number.

The dial impulses are. repeated by the relay 9 whose circuit, is closed via the contact of the said dial: earth, lower winding of 9, wiper a of the. make and break switch in positions 6 to 10, or wiper d. in position 11, TISS, tip p of the jack J I; and of the plugy of' the cord circuit and the dial in the cord circuit to battery.

Each time the relay 9 energizes,v it connects the conductors Li-Lz to the'y generator GI, and an A. C. dialling impulse is sent toA the distant exchange B.

The relay l is energized by the rst impulse of each train of impulses and holds during thev train of impulses', and dropv onlyA during the period between trains. of impulses. This relay drops only for a moment at the end of a train ofimpulses, and the line conductors L11-L2 are bridged through TTI- in order to discharge the line and thus. insure the; stable transmission of the impulses.

When the operator has completed dialling, the called number., she releases. the dial key which opens the circuit of the relay 5 through ring contact n, and relayv 5 opens at T5I the circuit of the. relay I6. The make and break switch advances by one step, the circuit of its magnet being closed Via.: earth, RI64, TI'5I, wiper b of the switch in position II, contact and' winding of the magnet, and battery.

The relay I6' is, again energized over its upper winding via: battery, upper winding of I6, wiper d of the switch in position 12, T|23 and earth.

The make and break switch is then advanced from position 12 to position 16, the circuit, of its stepping magnet being closed via: earth,cam Cai, wiper b in positions 12 to 15, TI63, magnet Cm; and battery.

The circuit of the relay 8 has been established via: battery, winding 8, THiS,l wiper d of the switch in positions 124 to 15, TI23, and earth. The relay 8 closes the circuit of relay `ilzwhich transmits an A. C. impulse to L1-Lz.

When the switch reaches position 16, the cir cuitA of the upper winding of the relay I 6 is opened, this relay opens at`TIB3 the stepping circuit of the switch, and at TI65 the circuit of relay 8 which drops and causes relay -9 to drop.

While the wipers of the make and break switch are moved from position 12 to position 16 under the control of the cam Cai, a long A. C. impulse (say '700 milliseconds) is sent to the exchange B.

If the called subscriber is engaged, the operator will notice the busy signal sent by the distant exchange. When the called subscriber lifts his receiver, a short impulse (say 100 milliseconds) is transmitted by the exchange B and is received on the relay 2 (Fig. 1) of exchange A. The relay 2 causes relays II and 4 to energize. Relay 4 closes the following circuit for the upper winding of relay I: earth, T4I, RI4I', r1*I'5I', TI54, upper winding of I5 and battery. As the two windings I5 are fed in opposition, the armature of this relay drops. The relay I5' is energized over its upper winding by TI5I', RI4I', T4I and earth.

At the end of the long impulse, the relay 4 drops, and the relay I5', whose upper winding is open, also drops. At RI53', the relay I5' shortcircuits the lower non-inductive high resistance winding of I. The cord circuit lamp indicator goes out, thus advising the operator that the called subscriber has answered.

The operator completes the call over the second plug of her cord circuit.

When the conversation is terminated and the called subscriber replaces his receiver, a short A. C. impulse is transmitted from the distant exchange B. It is received by the relay 2 (Fig. 1) of exchange A and causes relays I I and 4 to operate, as above described. The relay I5 is energized over its upper winding and is maintained in series with I5', as has already been shown. The lower non-inductive high resistance winding of I is short-circuited by RI53' which causes the cord circuit indicator lamp to light up, thus telling the operator that the call has been terminated.

When the operator removes the plugs, the circuit of the relay I is opened and this relay drops. The relay I3' is held by earth at TI2I. The relay I5 is energized on its lower winding via: battery, lower winding of I5, RIZ, TI2I and earth.

The stepping circuit of the make and break switch is established via: earth, cam Ca2, wiper b of the switch in positions 16-18. The relay 8 is energized in the circuit: battery, relay 8, TISS, wiper d of the switch in the positions 17 to 19, TI 23 and earth. The relay 9 is energized over TBI and the relay I over T93.

A long releasing impulse (approximately one second, for example) is transmitted to the ex change B by T9I and T92 during the time that the make and break switch is being moved to position I9. When the make and break switch arrives in position I9, the relay I2 is short-circuited by the wiper b and drops. The relays I6 and 8 drop, their circuit being opened at TI23. At TI8 I, the relay 8 opens the circuit of the relay 9 which drops and short-circuits at R93, the relay 'I which also drops. Relays I3', I5 and I5', whose circuit is open at TI 2|, drop.

The make and break switch returns to normal via the following circuit: earth, RI2I, wiper f in positions 12 to 21, contact and winding of magnet Cmi and battery. When the switch arrives in position 0, its stepping circuit is open.

vThe relay 3, whose circuit is again completed now available for i exchange B.

When the operator at the exchange A plugs in, the same operations as those just described occur until the iirst A. C. impulse is transmitted from exchange A to exchange B. The operator at exchange A then operates her calling key. The circuit of relay 2 is closed through the cord circuit via: tip p, RI32, relay 2, RI3I and ring n of Ji, The relay 2 closes at T2I the circuit of the lower winding of relay II which is energized. At TI I2, the relay II closesthe following circuit for the relay I6': battery, winding of I6', TI I2, RISI, RI23 and earth. The relay I6 closes at TISI' its holding circuit to earth at TI 2,

The following circuit for the lower winding of the relay I 6 is established: battery, lower winding of relay I 5, TI62', wiper c in position 1 and earth. When the relay IB operates, the circuit of the stepping magnet Cmi is established and the return impulse coming from the exchange B is received in the exchange A, as already explained.

When the make and break switch reaches position 11, relay I8 drops, its circuit being open in the Wiper e.

The make and break switch again steps and a long impulse is transmitted from A to B, as in the previous case.

When the operator at B replies, a short impulse is sent from B to A, and thus, as in the previous case when the called subscriber replies, operates the relays 2, II, 4, I5 and I5', and extinguishes the supervisory lamp of the operators cord circuit at A.

Before I 5 drops, relay I4 is energized in the following circuit: battery, winding of I4, TI 63', TI52', RI53 and earth. When relay I5' drops, relay I4 is energized in series with I 4 over TI 4I, and earth at TI2. The relay I 4 is energized in this circuit.

The two operators are now connected and` may route the waiting call.

When the call has been completed and the called operator at the B exchange replies, a short impulse (say 10) milliseconds) is sent from B to A and received on relay 2 (Fig. 1)

Relays 2, II and 4 thus operate, as has already been shown. A circuit for the relay I3 is completed over: battery, winding of I3, TI4I, T4I and earth.

The alternating current of GI is sent via T|3I and TI32 to the relay at the end of the cord circuit (not shown) which energizes and lights up the indicator lamp.

If the operator at the exchange A is calling by depressing her calling key, then relays 2 and II will be energized, as already shown. The following circuit is closed for the relay 8: battery, winding of 8, TI42, R62, TII5, R4I and earth, The relay 5 is energized by TBI and an A. C. impulse is sent to the exchange B over T9I and T92. The duration of this impulse corresponds to the time during which the retarded relay 6 is held whose circuit is closed at T2I The period during which this relay is held is increased by introducing a high resistance R3 in its circuit. When 6 energizes, it opens the circuit of relay 8 at R62, which drops and opens the circuit of relay 9, which also drops. The transmission of the impulse is com'- pleted even though the operator at A continues to press her calling key, since relay 2 and conse-v quently relay 6, remain energized while this key is depressed.

If the operator of exchange B removesthe plug, the same signal is given asin case of a call and, moreover, a busy signal is sent over the line.

When the operator at exchange A removes the plug, the release of the mechanism in Fig.y 1 takes place as previously described. When the relay I2 drops, it opens at TI2I the circuit' of relays I4,

I4 and I6,which drop.

In the case where the calling operator atv exchange A pulls out the plug before depressing-the dial key, or the calling'key, relay I drops, and relay I6 is energizedl over its lower winding through Rl I, the wiper e in positions 1 to' 10- and earth. The circuit of the magnet Cm'i is closed, as has already been shown at TIIi3,v andv the make and break switch will step eleven steps, sending a l'ong impulse toI exchange B.

Two conditions may arise:

(l) The return impulse from' exchange B is not received at exchange A. In this' event, relays,A I5, I5 and I2 are not energized. The make and break switch returns to rest position via RI5I, the wiper (b) of the` switch in position 1l, and over RI2I and the wiper (f) of the switch in positions l2 to 21.

(2) The return impulse lfrom exchange Bis received at exchange A. In this event, the relays I5 and I5' are energizedover Ti52, RI2; RII, wiper e` ofthe make and break switch in positions 1 to 10, and earth. IIhe relay I2 is energized' over TI54' and held over T122'.

The stepping circuit of the switchisl established in position 11 by: earth, RIS', 'III5`I ,wiper b of lthe switch in position, Contact andv Winding of the magnet, Cmi and battery.

The relay I6 is energized over RIZ, T`I2I and earth. i

From the moment when the make a'n'd break switch advances from position ll, a' long impulse is sent from exchange A to exchange B, as has been shown when the operator releasesV herdialling key in the case where a subscriber is called from exchange B by the operator at A. This impulse is followed by another long impulse which eiects the release.

In the event that the operator at A pulls out the plugy after having depressed her dialling key, or during dialling, then the release-will take place in the same way asin the last case considered,

The'operation of the input or impulse repeating mechanism willnowy be described' with reference to Fig. 2. This mechanism is equippedgto func'- tion in conjunction with a recorder suchIl as that shown iny Fig. 3'. It routes they calls either towards4 an automatic switchboard or towardsI a group of operators ringing relays' (Figa),

Assuming that a call emanating from exchange A is received at exchange B, when the operator at exchange A plugs into the jack of a disengaged tolli circuit, a long impulse (say, for example; 700 milliseconds) is sent from A to B, as has already been explained; This impulse isreceived by relay 2v (Fig. 2) over theI conductor L!y (Fig. 1'), Rl32", conductor A, RIM` (Fig.` 2'), RIIZT,x R183, R165; winding; of relay' 2, RI-SI',1 RI'IZ'-, condi'ictor B, RI3I (Fig. 2) and'lin'e conductor L2;

At' R2I, the relay 2 opens the following circuit ofthe relay 3' which drops: battery, windingoB', R4I', REI, RLI and earth'. The outgoing equipment (Fig. l) associated with the input mecha'- nism of Fig'. 2, is made' busy in` consequence of theopenine at T32 (Fig. 2) of triey circuit ofiit's relay 3v (Fig. l), as has already been explained. The relay 5 is energized in the circuit: earth, RBI, upper winding of 5, resistance R2 and battery.

When the impulse from the exchange A is completed, the relay 2 drops and the relay I is energized via: earth,.R2I, T5I, resistance R4, winding of I and battery. TheV relay 4 is energized by the earth at TII and the relay I5' over that of T45. At T52, the starting circuit of the generator G2 is completed. The starting circuit which operates the register findersCo3` (Fig. 3) is completed. over: starter' wire, MM', R34, RIIII, T45 and earth.

When the wipers of oneof the disengaged register nders reaches the bank contacts to which the mechanism shown in Fig. 2 isconnected, the circuit for the relay which stops the nder is establishedjvia: battery, resistance R5, T42, R35, RIIiand wire p towards the finder bank contact. The iinder, stops, as will be explained later, and batteryis applied through the register finder to thewire q.. The relay I6 is energized in the circuit: battery, on wire q, relay I6', RI44, T45 and earth. The relay I4 is' energized by battery windin'g'f I4, Tl'64, T45 andearth. The holding circuit of the relay I6 i's closed via: TISS, R206', T45 and earth; and that of the relay I4 via TIM', T45 and earth.

The relay Il is energized in the following circuit: battery, resistance R6,- winding of Il, RI9I,

RBI, TI4I, T45 and earth.y The relay I" ergized via-1 battery, resistance RT, windi I2, TI I`I',TI I2,RI9l,R6I,TI4'|,T45'and ear The relay I9 is energized via: battery, upper winding of I9, RI92, TI23', TII2, RIQI, RSI, TI4I, T45 and-earth.

The' relay II, whose windingA is shoit-circuited by TI'IZ and TI25, drops. After II' has dropped and has thus opened TI I2, the relay I9 is energized and I9' is held in the following circuit: battery, upper winding of I9? and I9', TIQI, T45 and earth.

The circuit of the relay I2 is opened at TII'Z', but this relay, Whose winding is short-circuited by TI26 and RII l, is retarded in releaseV and drops only after'a little while. While the relay II is attracted, ashort A. C. impulse (say milliseconds) is transmitted by T|24 and TI2'I over the line' conductorsl from the exchange A to the exchange-B.

The following starter circuit for the preselector Go2is established:- battery, magnet Cm2l of Co2, TI42', 'IFI-43, RIOI, R205', wiper T1 of Co2' and earth on the bank contacts corresponding to the junction' lines leading to the engaged automatic switch. When the wipersof Co2 arrive on' a disengaged junction line, then the wiper T1 will not iindan earth and relay I0' is energized inthe following circuiti earth', R205, winding of I0, T- I 42, Cm'2 Vand battery.

The relay' I0r opens at RIllIf the stepping circuit or the: preselector. At TIllI, ity applies on earth to: the bankcontact t0A mark the junction line engaged.

When the' operator at the exchange A dials the called number', A. C, dialling impulses will be snt'from A to B;

In the input equipment of Fig. 2', these impulses are received in' the' relay 2 throughA the circuit: conductor L1! (Fig. 1), R132', conductor A, RI24 (Fig. 22) RI 12", RI'83", resistance R3, relayZ', RI 8I", RI'I'2', RIZ I', conductor B, RI'SI (Figi. 1),.cond'uctor Lz.

The impulses receivedv by r'ela'y'2 are repeated 9 by the relay I whose circuit is cut at R2I at each attraction of 2. They are retransmitted to the register (Fig. 3), via: battery, R8, RI2, TI62 and wire 1'.

The re-transmission of the impulses by the register takes place over the following circuit: conductor A of preselector Co2, TI 05, TI63, wire t, impulse cam of register, wire u, TI 6I, Tl2, wiper b of Co2.

When dialling has been completed and the operator at the exchange A has released her dialling key, a long impulse is sent from A to B, as has already been explained, to operate relay 2. At R2 I, the relay 2 opens the circuit 0f the relay I, which drops. The battery through the resistance R8 is applied via RIZ and Rl92 to the wire r of the register.

When the register has completed the re-transmission of the called number, the circuit of relay I8 is opened in wire q, and this relay drops. The register is released, as will be explained below.

The relay 9 is energized in series with the feed relay of the junction linev through the following circuit: wiper a of Co2, TIGS, RI83, R203', lefthand winding of the relay I, lower winding of relay 9, RZDI', RI6I, 'IIZ and wiper b of Co2.

The relay 'I whose'right-hand winding is fed by R206' and T45, is not energized on account of the direction of the current in its left-hand winding. When the called subscriber replies, the direction of the current is reversed in the left-hand winding of 'I, and this relay operates and at TII it closes the circuit of the relay which energizes.

The relay II and, consequently, the relay I2 are energized in the following circuit: TI9 I T6 I, TUI I, T45 and earth. The lower winding of relay I9 is fed via: battery, lower Winding of I9, TI92, TI23, TI I2,TI9I',T6I,TI4I,T45 andearth. The llux created by this winding causes the relay I9 to drop.

The relay I 9' remains up and relays II-I2 drop, as has been shown in the foregoing. During the time that the relay I2 is held, a short A. C. impulse is transmitted to exchange B.

When the relay I2 has dropped again, the relay I 9 drops, its circuit being opened at TI23.

The speech circuit is completed via: conductor L1 (Fig. 1), RI32, conductor A, RI24 (Fig. 2), R572', condenser C2, RISS, TI95, wiper a of Co2, automatic switchboard equipment, line and staw tion of called subscriber, wiper b of Co2, TIM, RlGI, condenser C3, RI'I2, conductor B, RI3I (Fig. 1) and conductor L2.

At the close of the conversation, when the called subscriber replaces his receiver, current will flow again in the left-hand winding of relay I and the relay drops, opening at T'II the circuit of relay 6, which also drops.

The circuit of relays II and I2 is again closed and these relays in common with relays I9 and i9', operate. While relay I2 is held, a monitoring impulse is transmitted from the exchange B to the exchange A to indicate to the operator at exchange A that the called subscriber has replaced his receiver.

When the operator at exchange A removes the plug, a long impulse is sent to exchange B and is there received on the relay 2 (Fig. 2). At R2I, the relay 2 opens the circuit of the relay I, which drops.

Relay 5 drops again, its upper winding'being short-circuited via: earth, RII, T44 and RI 51.

When the impulse from A is received, and relay 2 drops, relay 4 is short-circuited via: earth, R2I REI and T4I. When relay 4 drops, it opens at 10 T45 the circuit of relays I9, I9', I5, I4, 20 and if necessary The relay I9 drops, its circuit being opened at TI42.

The incoming mechanism is freed. The relay 3 is held by R4I and R2I and at T32 Closes the circuit of relay 3 of the outgoing mechanism to operate the disengaged indicator lamps.

In the case where the operator of exchange A calls the operator of exchange B, the operations previously indicated in the case of the call from the subscriber takes place until such time as the preselector Co2 stops on a disengaged junction line leading towards the automatic switchboard.

The operator at exchange Athen operates her calling key, and thus, as has already been explained, transmits a long A. C. impulse from A to B.

This impulse is received on relay 2 (Fig. 2), relay I drops, its circuit being opened at; R2I. At the end of the impulse, re1ay 2 drops again. `At this point a battery is applied in the register to the wire r, as will be explained below. The following circuit for the relay is closed: earth, lower winding of 29, TIZ, TISZ'and battery on the wire r. The relay 29 opens at R295 the circuit of relay I9, which drops. The following circuit for relay 9 is established: battery, upper winding of 9, T296, Rland earth. The relay 29', which is no longer short-circuited at R92, is then energized, and is held in series with the upper winding of the relay 25 by T204, T45 and earth.

The circuit for starting up the preselector Co2 is established via: battery, electromagnet` C7122,

f contact 'of the electromagnet, TI42, TIM, RIIlI,

T295', wiper T2 and earth on the corresponding bank contacts to the junction lines leading to the automatic switchboard. All the bank contacts associated with the wiper T2 are connected to earth for all the positions which correspond to the junction lines leading to the automatic switchboard.

The wipers Co2 advance, therefore, over all the contacts of the junction lines to the automatic switchboard and over the bank contacts corresponding to the disengaged lines, and arriveon the bank contacts of the junction lines leading to the groups of operator calling relays. An earth is applied to the terminal corresponding to wiper T2 for all the engaged lines. When the wipers of Co2 reach a disengaged line, the earth on the wiper T2 is removed and the relay I9 is re-energized via: earth, T294', relay I9, TI42, contact of the magnet C1112 and battery. Relay I9 opens at RIBI the stepping circuit of Co2, and at TIGI applies earth to the wiper T2 to hold the line.

When the operator at exchange B replies, the wiper TI is earthed, as will be explained in what follows, and via T2ll2' and TIG3 closes the circuit for the relay EB, which is energized.

Relays II, I2, I9 and I9' operate in the same way as when the called subscriber answers. A short monitoring impulse is transmitted from B to A to inform the operator at A that the operator at B has answered. The speech circuit is set upyia: conductor L1, (Fig. 2), conductor A, RIM, (Fig. 2'), RITZ?, Tt', RIGS, T505, wiper a, operators station via the relay group (Fig. 4), wiper b of Co2, TIUZ, Rll, T29I, RI'iZ, RI2I, conductorB, R'ISI' (Fig. l) conductor L2.

On the completion of the dialling, whenthe operator at B removes the plug, earth is cut yoff the Wiper TI of Co2, as will be explained in `what follows, and the relay 6 drops, causing relays II,

I2,'9 and I9' to operate, as before, and transmits to the exchange A a monitoring impulse. VThen the mechanism is released on the reception of the release impulse coming from A, as in the case of acallfrom a subscriber at 'B Via the operator at exchange A.

When a communication has been established between the switchboards of the operators at A and B, and the operator at A, whom we are assuming to be the outgoing operator, makes a call by operating her calling key, a short impulse is transmitted from the exchange A to the exchange B, and is received on the relay 2 (Fig. 2) through the circuit: .conductor L1, RI32 (Fig. 1), conductor A; RI24, RI12, RIBS, RI65, relay 2, RIBI, `RI12, RI2I, conductor B, RI3I' (Fig. 1) and conductor Lz.

At R2I, the relay 2 opens the circuit of the relay I which drops. The following circuit for relay I`I is closed: earth, lower winding of I1, T202, RIZ; resistance R and battery. The relay 2, whose circuit is opened at RI12 and RI 12 drops, the relay I1 is held by its upper winding over TI1I and TI 52. The following circuit of the relay I8 is closed: lower winding of I8, TI1I, TI5I, R2I and earth.

Before the completion of the impulse, the relay 2 is re-energized in the following circuit: conductor Li, RI32 (Fig. 1), wire A, RI24 (Fig. 2), T46, TI83, RISE, winding of 2, TI8I, RIZI, conductor B, RI3I (Fig. 1) and conductor L2. The relay I5 is short-circuited at TI15 and drops again. The relay I1 is maintained on its lower winding over`T202, RI2, resistance R8 and battery. The relay I8 is maintained on its upper winding over TIBI, TI1I and earth.

An'alternating current impulse is transmitted f to the relay group .of Fig. 4 via: generator G2, TI13, TISZ, T203', RI63, TI05, wiper o. and bank contact, equipment'of Fig. 4, wiper b, TIZ, RI 6I, T20I, TIB2, TI13, and generator G2.

When the impulse from exchange A has been received, the relay 2 drops, and the relay I is reenergized. The relay I1 drops, its holding circuit being open at R12. At TI1I it opens the circuit of I8, which drops. 'Relay I5, which is no longer short-circuited at TI 15, is again operated.

The impulse transmitted to the equipment of Fig. 4 is completed, the transmission circuit being opened-atTI13 and TI13.

'Where, in the course of a conversation, the incoming operator in exchange B calls, a short impulse is transmitted by the equipment of Fig. 4 (as will be explained in what follows) and is received in Fig. 2 via: bank contact and wiper a, TI05, RISB, T203', TI05, RI63, T203', T105, RIBS, T283', RI83, Ri55, winding of 2, RI8I, 'I20I, RIGI, TIG2, wiper b and bank contact. The re* lay 2 opens the circuit of relay I, which drops. The circuit of the lower winding of relay I1 is Acompleted at RI2 and this relay at TI1 shortn circuits relay I5, which drops.

A short alternating current impulse is transmitted to the exchange B via: generator G2, TI13, RI82, T46, RIZII, conductor A, RISZ (Fig. 1), conductor Lz, apparatus of Fig. 1 of exchange A, conductor Lz, RI3I', conductor B, RI2I (Fig. 2)., RI.82,TI13generator G2.

'This impulse is received on the equipment 'of Fig. 1 at the exchange A, and as already explained, signals the operator.

When the reception of the impulse in Fig. 4 has been completed, relay 2 (Fig. 2) drops. The relay I is re-energized. The relay I1 drops and 12 the relay I5 is re-energized. The transmission of the impulse to the exchange A is completed.

If an input equipment is inadvertently seized, it immediately engages the corresponding outgoing equipment. A recorder is connected and a short return impulse is sent. lThis short impulse cannot cause the incoming equipment'at'the dis* tant exchange to be connected.

Two cases can arise:

(l) The outgoing equipment of the distant exchange which is not engaged is, nevertheless, seized by an operator. The repetition of the impulse sentby the distant exchange will cause the release of the recorder (impulse operating as upon the completion of dialling) the release of the circuit, and iinally the normal connection of the circuit.

(2) The outgoing circuit remains disengaged. After a certain lapse of time, an earth will be applied in the register (as will be explained in what follows) to the wiper L, and will, through the wire s short-circuit Via TM5 (Fig. 2) the relay 5. The relay 5 drops and opens at T5I the circuit of I which drops and short-circuits via R2I, RSI and `TIII the relay 4, which also drops.

The release is then effected as before. The release of the register occurs after the opening ci T45 and the circuit of the maintenance relay is opened in the line q and the wiper M.

We shall now describe, with reference to Fig. 3, the operation of the register which is provided to operate in conjunction with the incoming equipment to insure the correct re-transmission of the dial impulses to the automatic switchboard of the incoming exchange,

It has been explained in connection with the operation of-the incoming equipment ofFig. 2 that when said equipment is contacted, earth is applied to the starter wire MM of the registers.

The following circuit is completed for each free register: earth on wire MM, wiper ff of C04 in position 0, Fig. 3, wiper fb of C05 in position 0, RIZS, upper winding of relay 1 and battery. Relay 1 completes the following circuit for the magnet Cm3 of the register finder C03: battery, magnet Cm3 and its contact, TTI, R, R21 and earth.

When the wipers of C03 reach the terminals of the input equipment in use, the following circuit for relay C is completed: earth, R2I, T13, lower and upper windings of 6, wiper T, wire 1J and battery Via the apparatus of Fig. 2.

At RSI, the relay 6 opens the stepping circuit of the magnet C03 which stops. At T62, it completes the .circuit of the lower winding of the relay 1 in parallel with the lower winding of 6. The two windings of relay 1 being in opposition, its armature drops. The circuit of the upper winding of the relay I2 is completed as follows: earth, T63, R12. The relay 6 is held by TGI.

The circuit of relay I2 .is completed over its lower'winding via: battery, lower` winding of I2, R2II, TI25, wiperM .and earth on the wire q through the incoming equipment.

The relay 6 drops, the battery being disconnected from the wire pin the input equipment. The following circuit of relay 2 is completed: battery, resistance RIU, winding of 2, R53, TI 24, RI3, R62 and earth.

The register (Fig. 3) is now connected with the incoming equipment (Fig. 2) and the transmission signal is sent to the calling exchange via: R5I, TI22, wiper IE, wire r and-through the incoming equipment.

When the outgoing operator dials the called number, alternating current impulses are received on the incoming equipment (Fig. 2) and are retransmitted on the wire r of the wiper IE of C03 (Fig. 3). At each impulse, the relay is energized in the following circuit: battery on the wire r in the incoming equipment, wiper IE, TI22, winding of I, R4I, RIII, TI2I and earth.

The circuit of the relay 4 is established: battery. winding of 4, TI2, TI23 and earth. The relay I is maintained by TI I. When relay I drops again the relay 4 is maintained by T42, TI2I, contact of the electromagnet Cm4 and earth. After the relay I has been released, the relay 3 is energized in the following circuit of its upper winding: battery, upper winding of 3, R32, T23, T43, T25, RIZ, TI23 and earth. The relay 3 sticks, and via T33 completes the following circuit of the relay 5: battery, winding of 5, T33, TI2I and earth. The relay 5 is held and via T52 closes its holding circuit.

The circuit for the magnet Cm4 of the contactor C04 is closed as follows: battery, magnet CmII, T32, T23, T43, T25, RIZ, TI23' and earth. The magnet Cm4 attracts its armature and opens the circuit of the relay 4 which drops again. The relay 4 reverts to non-operating condition, opens at T43 the circuit of the magnet Cm4 which releases its armature, thus causing the wiper of C04 to advance by one step.

When, under the action of the following impulses, the relay I pulls up, the relay 4 is re-energized at TI 2 and completes the circuit of the magnet Cm4 which attracts its armature, opens the circuit of relay 4 which drops again, and thus causes a new advance by one step of the wipers of C04.

The same operations are repeated for each dial impulse received on the relay I, causing the advance of the wipers of the switch C04 by one step.

The relay 3 is held for the duration of each series of impulses by T3I, its lower winding being short-circuited by RI I and R4 I. A moment after the end of each impulse series, the relay 3 drops. The charging circuit of the condenser which is connected to the bank contact of the wiper d of C04 and on which said wiper is stopped at the end of the impulse series, runs through: battery, parallel winding of the relay 2 I, TI25, R34, wiper d, condenser, resistance RII and battery.

The same operations are repeated for each se-` ries of impulses, as many condensers being connected to the bank contacts of the wiper CZ as there are digits in the number received.

The re-transmission of the impulses will now be explained.

The selector of the automatic switchboard is connected with the register through the incoming equipment over the following fundamental circuit loop: wire t, wiper A, TI22, R252, TI23, wiper B, wire q. Relay 9 is energized by its upper winding over R92 and this loop and locks up over its lower winding and TSI to the earth at TI2I.

When the rst digit has been registered, the following circuit of relay 24 is closed: battery, resistance RI2, winding of 24, R23I, T93, R2I2, T54 and earth. The relay 24 closes the following circuit for relay 2E: battery, winding of 25, T242, R23I, T93, R2 I2, T54 and earth.

Relay 24 is short-circuited at T232 and drops. Relay 26 is held by T233. The energizing circuit of the relay 28 is closed at T23I and R243. When cam K2 is opened, the circuit of relay 25 is completed through: battery, series winding of 25, T282, R22I, T283 and earth. The stepping circuit of the magnet Cm5 is established through: battery,

14 magnet Cm5 of C05, T25I, cam K2, T282, R22I, T283 and earth.

At R252, the cam KI is disconnected and introduced into the above traced circuit of the selector. When the cam is opened, animpulse is transmitted to cause the selector tc operate.

When the wipers of C05 reach the bank contacts which correspond to the bank contacts of C04, on which the wipers are first stopped, the condenser which has been charged is discharged through the wiper a and the winding of the relay 22. This relay is energized and locks up over T22 I and earth at T283.

The circuit of the magnet Cm5 is opened at R22I and the switch C05 is stopped. The relay 25 is held and the relay 23 is energized over the following common circuit: battery, series winding of 25, T282, winding of 23, T283 and earth.

The cam K1 is short-circuited at T232 and the circuitof relay 261s opened at R23 I. When the relay `23 drops again, the relay 28 drops in its turn, its circuit being opened at TZEI. At T283, relay 28 opens the circuit of relays 22, 23 and 25, which drop.

It will be seen that the same number of interruptions are produced in the fundamental circuit as there were impulses in the rst digit of the number received on the switch C04. The wipers of C05 have been stopped in the position which corresponds to therst position in which the wipers of C04 stopped.

The registering and re-transmission of the other digits of the called subscribers number takes place in the same manner.

When the -operator at the outgoing exchange has completed dialling, she opens her dialling key and a long impulse is transmitted to the incoming exchange. This impulse is received in the incoming apparatus and causes relays I and 4 of the register to be attracted (Fig. 3). The relay 2 drops. When reception of the impulse has been completed, relay I drops, but relay-2 cannot again energize, its circuit being opened at R53.

When the last digit has been re-t-ransmitted, the wipers of C05 will have caught up those of C04, whereupon the relay 2l will be energized in series with '22 in the circuit: TI25', R34, wiper d of C04, wiper a of C05. At R2I I,-the relay 2| opens the circuit of the relay I2 which' includes wire q and wiper M of C03. The relay I2 drops, and at TI2I opens the circuit of the relay 4, and at TI25, the circuit of relays 2| and 22, which drop.

The following circuit is closed for the return to rest position of the switch C04: battery, magnet C`m4, wiper ff on the sectors f, RI2I, contact of magnet Cm4 and earth. When the wipers of C04 reach position 0, the circuit is opened.

The switch' C05 returns to rest position via the circuit: battery, magnet Cm5 and its contact, sectors b and wiper fb, RI2I and earth.

In the event that the operator at the outgoing exchange wishes to communicate with the operator at the incoming exchange, the same connecting operations take place that have been previously indicated, and an idle register is connected with the incoming equipment.

However, instead of operating her dialling key, the operator of the outgoing exchange operates her calling key, and a long A. C'. impulse is transmitted to the incoming exchange. This connects battery to the wire r, as has already been eX- plained before. The following circuit for relay I (Fig. 3) is closed: battery, on the wire r, wiper IE, TI22, winding of I, R4I, RIII, TI2I and earth. .At'TI I, theY relay `I closes its holding circuit. At TI2, it closes the energizing circuit of relay 4: battery, winding of 4, TI'2, TI23' and earth.

Relay 2 is short-circuited by T13 and R62 drops, and relay I2 is held by R2I I. The following circuit of relay I I is closed: battery, winding of II, R23, T43, R and earth.

When the impulse has been received, relay I drops again, battery being cut off the wire r in the incoming apparatus. Relay 4 is held by T42, TI 2 I contact of the magnet Cmd and earth. Relay 2, which is no longer short-circuited at TI`3, is re-energized, and relay II Vis held over TI I I, TI2I and earth.

Battery is then `applied to the wire r through: battery, resistance RI3, R55, TII2, T26, T122', wiper IE of C03 and wire 1'. This battery in the input apparatus, as has already been described, causes the orientation of th'e preselector Co2 (Fig. 2) on to a disengaged operators position.

The holding circuit of relay I2 is opened in the incoming equipment on the wire p, and the relay drops again opening at TI2I, the circuit of 4 which opens at TI'2I the circuit of II, which alsodrops. Relay 2 drops again, its circuit being opened at TI2I and TI24.

When the register (Fig. 3) is connected, relay 21 is energized through: battery, upper winding of 21, TI26 and earth through cam I, while said cam is closed. This relay 21 is then held attracted on its lower Winding through: battery, lower Winding of 21, T212, R24I, R33, TI2I and earth. If the dialling is then carried out normally the holding circuit is cutI at R33 or R24I and the relay 21 drops. If, on the other hand, the dialling is not carried out, or if the time which elapses between the reception of two successive series of impulses is too long, then after a, certain time (depending on the cams) the relay 21' is energized, when the cam 2 operates through TZ'II and its upper winding. It is held on its lower Winding by T21I, TI2I and earth. Via TI2I and T212' earth is then applied through the Wiper L of C03 to the wire s, which causes in the input apparatus, as already described, the holding circuit of the relay I2 to be cut off the wire 2 and, consequently, the release of the register.

We shall now describe with reference to Fig. 4 the operation of the group of relays by means of which the .calls intended for the incoming operator are routed from the incoming apparatus.

When, as h'as already been explained, a preselector such as Co2 (Fig. 2) stops in the position corresponding to the group of calling relays of Fig. 4, earth is applied to the wiper T2 and the corresponding bank contact. The circuit of relay 1 is completed over R1 I', and this relay completes at T13 the circuit of the calling lamp LA of the operator.

The return signal from the called subscribers is Vsent via T12, R82', bank contact and wiper A and via T1 I, R82, bank contact and wiper B.

The operator advised of the call by the lighting of lamp LA plugs one of h'er cord circuits into the jack J4. The circuit of the relay 6 is closed at R13 to earth applied to the sleeve of the jack J4 through the cord circuit. The relay 6 closes vie, T61 and T65 the circuit of the relay 1' to earth on Wire T2. When relay 1 energizes the relay 6 is held over T64. The relay 1 whose circuit is opened at R1I, drops. At T63, relay E completes the circuit of relay I, which operates.

Through T52, earth is applied to bank con- 16 tact and wiper T2 :to lcontrol in the incoming equipment the supervision of the call.

The connection is established over the lwiper and bank contact A, R82', tip of the jack, cord circuit and station of the operator, ring of the jack, R82, bank Contact and wiper B.

When, in the lcourse of a call, the incoming operator wishes to call the outgoing operator, she operates her dialling key. The circuit of relay 2 is closed via the tip of the jack i4, R43, relay 2, R42 and ring of the jack J4. lAt TZI, relay 2 completes the circuit of relay "8 which opcrates.

An A. C. impulse is transmitted tothe incc1ning equipment (Fig. 2) in order, as has already been explained, to cause transmission of an A. C. impulse to the outgoing exchange: generator G5, T33', R32, R44, T65, T14', bank contact and wiper A, incoming apparatus, wiper and bank Contact B, R46, RSI, T83, :generator G5. The duration oi this impulse is fixed by the time required for the attraction of the relay 3 Whose circuit has been closed at T84 and R45. As soon as the relay 3 is energized, the impulse terminates, the transmission circuit being opened at rR3I and R32.

The purpose o this arrangement is the sending of a short impulse to thel outgoing exchange, irrespective oi the length of time it takes the operator to manipulate the dial.

The relay I which is shcrt-circuited via earth, T63 and T84, drops again. When the operator releases the dial, the relay 2 drops, opening at T2I the circuit of the relay 8, which also drops. The relay I which is no longer short-circuited at T84, is energized again. The relay 3 drops again, its circuit being opened at T84.

The line is released before the relay 8 has dropped completely, Via the following short circuit: wiper and bank contact A, T14', T65, R44, R32, R85', RIS, R46, bank contact and Wiper B.

When, in the course of the call the outgoing operator calls the incoming operator, a short A. C. impulse energizes the relay 2 in the fol1owing circuit: Wiper and bank contact A, R32', R43, winding of 2, R42, R82, bank contact and wiper A. Relay 2 closes via T2I the circuit of relay 8, which at R82 and R82 opens the circuit of 2. The relay 8 is held at TII and earth on TSI. The following circuit of the relay 4 is closed: battery, upper winding of 4, TBI', TI2, R2I and earth.

During reception `when the impulse has been completed, relay 2 is re-energized in the following circuit: wiper and contact A, T14', T65, T43, Winding of 2, T42, bank contact and wiper B.

Relay I, short-circuited at T84, drops again.

Relay 8 is held at T21. and T81.

An A. C. impulse is transmitted t0 the operators cord circuit via: generator G5, T83', R32, T44, tip of the jack J4, cord circuit, ring of the jack J4, T46, RSI, T83 and generator G5. This impulse energizes the relay at the end of the cord circuit and thus lights up the terminating lamp in order to inform the operator of the call.

When the impulse has been received, relay 2 drops, opening at T2I the circuit of relay 8y which also dro-ps, opening at TBI the circuit of 4, which drops.

The re-energization of relay I and the release of the line take place in the manner already described.

When, upon the completion of a call, the outgoing operator removes the plug, the impulse Relay-4 is held at T4I 17 received on the incoming equipment causes the release of the equipment and the earth will oc removed from the wiper and contact T2.

Relay 5, short-circuited at T66, is then energized in series with the relay 'I' which is held at T61. Relay 5 completes via T54 and T63 the holding circuit of its lower winding. Earth is applied to the bank contact and wiper T2 at T5I and T66, in order to insure continued hold# ing of the group of relays in the banks of the preselectors.

The relay 'I' is held at T61 and T5I. The busy signal is sent to the incoming operator via T53, R82', tip of jack J4, cord circuit and operators station, ring of J4, R82 and T52.

When the incoming operator removes the plug, relay 6 drops again, its circuit being opened in the sleeve of the jack J4. At T63, the relay 6 opens the circuit of relays I and 5, which drop. At T5I, relay 5 opens the circuit of the relay 7', which drops.

If the operator at the incoming end is the rst to unplug, then the relay 6 will drop after this cut-off operation has taken place, its circuit being opened in the sleeve of the jack.

The relay 'I is held via T'II' and earth on the terminal and wiper T2. The incoming equip ment transmits an impulse by cutting off earth at T62 from contact and wiper TI.

The busy signal is sent to the calling end via: R55, T14', .contact and wiper A and via RSI, T12 and contact and wiper B.

When the incoming equipment is released, the earth is cut off contact and wiper T2, and the relay 'I' drops again.

If the toll boards of an exchange are so equipped that the operation of the dial does not operate switches in the outgoing equipment of Fig. l, the outgoing equipment of Fig. 5 will be substituted.

This equipment comprises two make and break switches, driven successively vby the magnets Cm! and Cm2. The wipers of the make and break switch Cm! are designated by capital let ters and those of the switch Cm2, by small letters. Thus (NA) indicates that this contact is closed by the wiper A of the make and break switch CMI in position il, and o(a) that this Contact is closed by the wiper a of CM2 in position o.

The switch CMI receives locally the first series of impulses which determines the total number of impulses t'o be sent by the operator. Assoon as the impulses have beentransrnitted, the outgoing equipment will automatically send t the incoming exchange, a long impulse indicating the completion of dialling. This replaces the impulse which was sent in Fig. 1 when the operator released her dialling key.

When the equipment is free, relay is energized in the following circuit: battery, winding `of 5, wiper (a) of the switch and CM2 in the position o, wire'c and earth through I', incoming equipment. .The circuit of the disengaged lamp In is closed at T52.

After having insured that the equipment is disengaged while operating the lighting up lever Lr, the operator plugs one of her cord circuits into the jack J i. The following circuit of relay 3 is then closed: battery, series winding of i'-, Rl25, T5| and earth on the sleeve of jack Ji through the relay of the third wire of the cord circuit whose indicator lamp has been extinguished. At T3I, relay 3 completes thecircuit of relay 4 through the resistance RI `Relay 4 closes 18 its holding circuit via T42 and at T43 completes the circuit of relay 25, which is energized. At R25I and R252, relay 5 disconnects the outgoing equipment of Fig. 5 from the incoming equipment of Fig. 2.

The following circuit of magnet CM2 of the y flrst switch is closed: battery, magnet cm2 and its contact, wiper (c) of switch cm2 in the position o, T32 and earth.

The switch cm2 advances by one step. Relay 5 drops again, its circuit being opened at the wiper a, which has left position o. Relay 3 is operated via T44. lThe following energizing circuit for relay 6 is then closed: battery, lower winding oi 6, wiper e in position l and earth. At TBI, relay 6 completes the following circuit of relay 2I battery, winding of 2l, resistance R2, TGI, wiper a in position 1 and earth. At T2I3, relay 2l completes the circuit of relay 23.

A long holding impulse of alternating current is vtransmitted in the holdingcircuit via: generator ,and G, T2ll, T25I G, T2I2, T252, conductor LI and conductor L2.

The stepping circuit of switch cm2 is completed via: battery, magnet cm2, T62, wiper c in position 1, interrupter Cal and earth. The switch cm2 advances step by step and the impulse is continuously transmitted over the inter-urban circuit. i

When the switch cm2 arrives in position, the circuit of relay I, through wiper a is opened. This relay falls off and at T2I2 and T2I I, opens the impulse circuit ending the transmission ofthe impulse. The relay 23, short-circuited atR2I3 falls, but only a moment afterthe dropping of 2 I, which permits the release of the line by shortcircuiting at T232.

The switch cm2 continues to advance in the circuit: battery, winding of cm2,l T52, wiper c in positions 5 to l0, cam Cal and earth. When the switch arrives in position l1, the circuit of relay 6 is opened. The make and break switch passes thls position via the circuit: battery, winding of cm2, wiper b in position 11, RIZI and earth. It then reaches itsrest position via wiper (f) inthe positions 12 to 20, and earth on RII .1

The same cycle of operations is repeated and the long impulses (about 700 milliseconds, for eX- ample) are transmitted over the inter-urban circuit to the called exchange, the successiveimpulses being separated by a iiXed interval'of time (about 1 second, for example), until Va return impulse is received from the incoming equipvment (about milliseconds, for examplelon relay 22 via the circuit: conductor LI, T252, R2 I2, R283, vwinding of 22, RZSI, RZI I, T25I and conductor L2. At T22I, relay 22 completes the cir- Cuit of the lower winding of relay 23 which at T283 and T28I, substitutes the relay 24 for relay 22. The relay 28 is held on Vits center winding via T24I and does not fall olf during the substitution of the relay 24 for relay 22 because itis retarded by its upper winding, which is shortcircuitedy at T284.

The following ycircuit of the `relay I2 is then completed: battery, lower winding of I2', RI22, R3I I, T24I and earth., At` the endof the reception of the impulse, the relay 24 d ropsfbut the relay I2 -is held on the following circuit in series with I2 which is energized: battery, lower winding of I2', lower winding of I2, TI22 T43 jand earth. At TI21, relay I2 completes the circuit of relay "I, which Vis held through T12.

The 'stepping circuit of switch cm2 is open Vat BIZI and the switch is held in position 11. Y

The relay 6 is held on the earth through `the Wiper f in position 11. The relay3 is held on its lower `winding through T121, its upper winding which has a 'high resistance is short-circuited at R125 causing the lighting up of the supervisory lamps of each of the operators dials in the wellknown manner.

The operator presses the dialling key and proceeds to dial the number of the called subscriber. This opens the holding circuit of relay v, which beats in the rhythm of the impulses. 'The step'- ping .circuit of switch `cm1 is completed each time the relay 3 is released: battery, electromagnet CM1, T124, R33, R112, T11 and earth.

The impulses are re-transmitted bythe relay 21 via the circuit: battery, winding of 21, resistance R2, T126, T63, wiper d in position ll, or wiper a in positions 6 to l0, R32 and earth. Through T211 and T212, the dialling impulse-s are repeated on the inter-urban circuit Li-Lz as alternating current impulses.

The iirst impulse which is received, energizes relay 23 via T213. This relay is held during each series of impulses, the short-.circuit around its winding vat R123 during the release of `23, retarding it sufficiently. Relay 23 drops off a moment after the completion of each impulse series.

It may be assumed that the called subscribers number has ve digits and that the rst ydigit is 1. The -make and break switch cm1 advances by onestep. When relay 23 drops, the following circuit of relay `1'1 is completed: battery, winding of 11, wiper A in Aposition 1, R231, R112, T11 and earth. As lsoon as R112 opens, relay 11 is -energized via R111", T113, wiper D in position '1, and earth. The switch cm1 advances to position 1l via the following circuit: battery, winding of CM1 and its contact, R1 13', T115, wiper D in positions 1 to 10 and earth.

When switch cm1 reaches position 11, it stops, its circuit being opened on the wiper D. Relay 11 is maintained in series 'with relay 1 1' which is energized in the circuit: battery, winding of 11, windingfof 1 1", T1 1 1, T43 and earth.

Ir the first digit of Athe called number differs from 1 (four-digit number, for example) the switch cm1 advances the same number of lsteps as there are digits in the 'number transmitted. In this case relay 8 is energized when relay 23 drops via the following circuit: battery, wiper A in position 2 to 10, R231, R112, T11 and earth. The said relay is 'held byV T81 on the earth of T43. Relay -11 is energized in the circuit: battery, winding of 11, R111', T83, wiper D in positions 1 to 10 and earth. The advance of switch `cm1 to position 11 and the holding of relays 11 and 11' takes place, as in the case where the first digit dialledwas 1.

Each digit following the rst, advances switch cm1 lby one step, `the circuit being completed `every time relay 23 is 'held via the wiper C in positions 11 to 14 and earth.

After the second Adigit has been dialled, the following circuit of cm2 is completed: battery, winding of cm2, wiper b in position 11, T123, T112' or T82, wiperB in vposition 15 or 14, wiper f in position 11 and earth. The make and break switch cm2 advances by one step, and passes to position 12. The relay 6 is held via: battery, upper win-ding of 11B, wiper d in position '12, T'11 and earth.

The stepping circuit of the make and break switch cm2 is completed via: battery, Winding o'f cm2, T62, wiper b in positions 12 Vto 15, cam Ca2 and earth.

The relay 21 is energized via: battery, winding of 21, resistance R2, T61, wiper d in positions 12 to l5, T'11 and earth. At T213, relay 21 completes the circuit of relay 23 which operates. The switch cm2 is stepped by cam Ca2, and while it moves a long A. C. impulse is transmitted on the toll circuit via T212 and T2 1 1.

When switch cm2 reaches position 16, the relay B drops, its circuit being opened in the wiper d. At T61, it opens the circuit of 21, which drops and short-circuits at R213 relay 23, which drops after a short time.

If the called subscriber is engaged, the operator receives the busy signal. If the subscriber is free, she receives the ringing tone.

When the called subscriber answers, a short impulse is transmitted by the called subscribers exchange to energize relay 22 which causes 28 and 24 to operate, as has already been explained, when 'the incoming equipment was connected. The following circuit for the upper winding of the relay 12 is completed: battery, upper winding of 12', T123', T122, R311, T241 and earth. This winding being in opposition to the lower winding, relay 12 drops again. The relay 12 is held on its upper winding by T122, R311, T241 and earth.

When the impulse has been received, relay 24 drops again, and at T241 opens the holding circuit of relay 12. After the relay 12 has been released, the upper high resistance winding of the relay 3 is put back into circuit, which causes the supervisory lamp of the cord circuit to be energized in the known manner.

Communication between the two subscribers may now be established.

When the called subscriber replaces his receiver, a new short impulse is transmitted by the equipment of the incoming exchange to operate relay 22 which causes the operation of relays 28 and 24, and the re-energization of relays 12 and 12', as has already been mentioned. At R125, the upper high resistance winding of the relay 3 is cut out, which causes the cord circuit supervisory lamp to light up. The relay 3 is maintained on its lower windingby T12 1.

When the calling subscriber hangs up, the relay 3 drops, its circuit being opened in the third wir@ of the cord circuit. Relay 4 is maintained by T42. Relay 6 is re-energized in the following circuit: battery, lower winding of 6, wiper d in position 16, R32 and earth.

The following circuit for the operation of the switch Cm2 is closed: battery, winding of Cm2, T62, wiper bin positions 16 to 18, cam Cal and earth. Relay 21 is re-energized via: battery, winding of 2|, resistance R2, T61, wiper d in positions 17 to 19, T11 and earth.

During the advance of switch Cm2 to position 19, a long release impulse is transmitted to the called subscriber via T212 and T211.

When the switch reaches position 19, relay 1 falls, its circuit being open in wiper b. At T'11, it opens the circuit of relays 6 and 21 which drop. At R213, relay 21 short-circuits relay 23, which drops.

The switch advances to position 21 via: battery, winding of CmZ and its contact, wiper .f in positions 12 to 20, R11 and earth.

Relay 4, short-circuited by R31 and wiper b in position 21, drops.

The switch cm2 returns to its rest position via R45 and the wiper f in position 21.

The relays 12, 12', 11, 11', 8 and 25 drop, their circuitbeing opened at T43'.

Relay 5 is re-energized through the incoming equipment via the wiper a in position 0.

When relay 4 drops, switch CMI returns to the rest position by the circuit: battery, magnet CMI and its contact, RII3', R46, wiper d in positions 1 to 20 and earth.

We shall now describe the operation of the equipment of Fig. 5 when the operator at the calling exchange wishes to enter into communication with the operator of the called exchange.

The course of the operations after plugging into jack J I, the transmission of the holding impulse and the reception of, the impulse in return, is the same as in the preceding case.

In order to call the operator at the called exchange, the operator at the calling exchange depresses her calling key. Relay 22 is energized by the calling current coming from the cord circuit via: tip of jack JI, R212, relay 22, R21I, and ring of jack J I. The circuit of the lower Winding of relay 28, and that of relay 26, is coml pleted at T22I, the circuit of relay I0 is completed: T253, RI|4 and earth, and this relay is held over T|I.

The stepping of switch Cm2 Via T62, the recep tion of the return impulse, and the energization of relays I2', I2 and 1 then take place in the same way as in the preceding case.

Position 1l of switch Cmi. is cleared by the circuit: battery, magnet cmZ, Wiper b in position 11, TI23, T|Il2, wiper f in position 1l and earth. The switch cm2 then advances to position 16, and a long impulse corresponding to the holding impulse of the Ydialling operation is transmitted to the called exchange, as in the preceding case. When the make and break switch was in position 11, the relay 3| was energized by the circuit: battery, winding of 3|', T|02, TIIIZ, wiper f in position 11 and earth. It is then held in series with 3| which is energized in the circuit: battery, winding of I3', winding of 3|, T3II, T43 and earth. v

When the operator of the called exchange answers, a short impulse is transmitted and causes, as in the preceding case, when the called subscriber answers, the energization of relays 22, 28, 24, I2 and I2 and of the supervisory lamp in the cord circuit.

In case of a recall by the called operator, a short impulse is transmitted by the called exchange. This impulse causes the operation of relays 22, 28 and 24. The circuit of the relay 21 is then completed: battery, winding of 21, T3| I, T24| and earth. Via T21| and T212, the current of the generator G is transmitted to the end relay of the cord circuit plugged into J1 and causes the lighting up of the supervisory lamp so as to attract the attention of the operator of the outgoing exchange.

If the operator of the outgoing exchange recalls the relays 22 and 28 are energized when the operator manipulates her calling key. The following circuit of the relay 2| is then completed: battery, winding of 2 I, resistance R2, T3|2, R262, T22I and earth. At T2 I3, relay 2| completes the circuit of the relay 23, which operates.

An A. C. impulse is transmitted on the toll circuit via T2I| and T2! 2. The duration of this impulse is determined by relay 26, which is energzed over T22I and resistance R5, and a moment afterwards over T26I. Relay 26 opens at R262 the circuit of relay 2l which drops and causes 23 to drop. The transmission of the impulse ends upon the release lof relay 2| even if the operator continues to manipulate her calling key.

When the called operator unplugs, the signal is given as in the case of a call, but in this case the busy signal is transmitted to the outgoing exchange.

Release takes place after unplugging the jack JI, as in the previous case. Relays 3|, 3| and I0 fall after the release of relay 4, their circuit being opened at T43.

In case the outgoing operator cuts oil" before dialling or operating her calling key, relay 3 drops. The relay 4 also drops, its winding being short-circuited at RSI, wiper D in position 0 and earth. Relay 6 is energized on its lower winding by the wiper ein position l, and earth. The switch cm2 advances to II and transmits the holding impulse.

Two cases may be considered:

(1) The return impulse is not received. In this case relays I2', I2 and 1 are not energized. The switch cm2 is released by the wiper b in position 11, and earth on R|2|, then by wiper f in positions 12 to 20 and R1I, and iinally by wiper f in position 21 and R45.

(2) The return impulse is received. In this case relay I2 is energized, is held in series with I2 through T|22, RM, wiper (c) in positions 1 tp 10 and earth. Relay 1 is energized by TI21 and is held by T12. The switch cm2 passes to position 1 via the circuit: battery, magnet cm2 and its contact, wiper b in position 11, TI 23, wiper A in posi tion 0, R43 and earth. Relay 6 is held by T1I, wiper d in positions 12 to 15, then by R32, wiper d in position 16 and, finally, by the wiper d in positions 1'7-19. A long impulse, as at the end of the dialling, is transmitted to the outgoing exchange, then another long impulse for the release.

In the preceding description, it was assumed that each of the interconnected exchanges has an automatic switchboard. If an exchange that has no automatic switchboard is called an exchange like that shown in Figs. 1 or 5, then, as is shown by the dotted line in Fig. '7 for exchange A, the equipment of Fig. 2 is replaced by the equipment of Fig. 6.

We shall assume that exchange A is called by exchange B. When the operator of the exchange B seizes the circuit, an impulse is transmitted by the outgoing equipment. This impulse is received on relay 2 (Fig. 6), via the following circuit: conductor LI, Rl32' (Fig. 1), conductor A, R|24, (Fig. 6), relay 2, RIZI, conductor B, RI3I (Fig. l), conductor L2.

Relay 3, which is normally held by R4I, REI, R2| and earth, drops when its circuit is opened at R2 I. 'I'he outgoing equipment is engaged when the circuit of the wire C is opened at T32.

Relay 5 is energized on its upper winding by: earth, R3I, upper winding of 5, resistance RI and battery. When the impulse has been received, relay 2 drops and the circuit of the relay I is completed: battery, winding of I, resistance R2, T5I, R2I and earth. At TI I, relay completes the circuit of relay 4 which is energized. The following circuit of relay I is closed: resistance R3, windingof I I, RISI, R6|,T42 and earth.

Relay I2 is energized in the following circuit: battery, resistance R4, winding of I2, TI I I, TI I2, RISI, RBI, T42 and earth. The circuit of relay I9 is completed by: battery, upper winding of I9, RIS2', TI23, T|I2, TISI, RBI, T42 and earth. Relay I, short-circuited by TI I2 and TI 25, drops. After TI I2 has been opened, relay I6 is held in the following circuit in which relay I9 is ener- 23 gized: battery, upper windings of I9 and I9', TIB-I, T45 `and earth.

The circuit of relay I2 is opened at Tl I2, but said relay is short-circuited by TI26 and RII! and is retarded. During the whole period oi the energization of relay i2, a short A. C. impulse is transmitted via TIZi and T124 and the relay I3 is energized. This relay, whose dropping has been retarded by its upper winding which is short-circuited at TISi, causes the line to be released aiter the drop of i2 by short-circuiting at I32.

When the operator at the outgoing end operates her calling key, a new long A. C. impulse is received at the incoming exchange and energizes relay 2 for the holding impulse.

Relay I, whose circuit -is lopened at R2I, drops.

The following circuit for relay I3 is closed: battery, winding of I3, R182', T44, Ril and earth. When the impulse has been received, relay 2 drops and relay I is re-energized. Relay I8 is maintained in series with relay I8' which is energized by TIBI and T45. The driving circuit of the preselector Col is completed as follows: battery, magnet Cml of Col and its contact, TII, TI83, RI il I wiper T2 of Co'I and earth on the bank contacts `of the junction line leading to the engaged incoming boards.

When the wipers vof Col arrive on the bank contacts of a free line, the earth on Wiper T2 is cut ofi'. Relay |18 is energized on its lower winding via: earth, lower winding of I9, TI 8 I contact and magnet Cm-'I and battery. The preselector Co'l stops, its circuit being .opened ai; RII D I.

A group of operators calling relays, such as those of Fig. 4, is then connected to the equipment of Fig. 6. The busying of the line is caused by earth of TI I on the `wiper T2.

The calling of the operator takes place as in the operation of the device in Fig. 4. When the incoming operator replies to a call, an earth is applied `to wiper TI by the equipment in Fig. 4. This earth energizes via Tlll relay 5, which completes the following circuit for relay I I battery, resistance R3, winding of I I, TI9I, Ti, T42 Iand earth. The relay I2 is energized on the same circuit by TI i2. The following circuit of the lower winding of relay I9 is completed: battery, lower Winding of I9, TI92, TI23, TII2, TI9I,

TSI, T42 and earth. The two windings 0i the l relay L9, being in opposition, said relay drops. The relay I9 is held in the same circuit through its lower winding.

While relay I2 is held, a short impulse is sent to the outgoing exchange. Relays II and I2 drop. Relay I9 drops, its circuit being opened at TI23. The call `is established via: conductor LI, RI32 (Fig. 1) conductor A, RI24 (Fig. 6) TID5, wiper A, equipment of Fig. 4 and incoming board, wiper B, TI02, RI2I, conductor B, RI3I (Fig. l), conductor L2.

When the call has been completed and the outgoing operator disconnects, .a long A. C. impulse is transmitted by the outgoing exchange to energize `relay 2. Relay I, whose circuit is opened at RZI, drops. Relay 5 drops, being short-circuited via: earth, RII, T44 and TI82.

When the impulse terminates, relay 2 drops. Relay 4 drops, being short-circuited via: earth, RZI, RBI and T4I. At T45, it closes the circuit of relays I and I8', which drop. At TIBI, relay I9 opens the circuit of relay I0, which drops. Relay 6 drops, its circuit having been opened at TI03. The relay 3 is re-energized by Rf-fIIl REI and R2I.

In the case where the incoming operator is the rst to disconnect, vthe circuit of relay 6 is opened in Wiper TI. In consequence of the operation ci rela-ys il, I2, I9 and I9', via REI and RIBI, a short supervisory impulse is sent to the outgoing exchange.

When the outgoing operator disconnects, the release takes place. Relays I9 and I9 drop after 4, their circuit being opened at T45.

The equipment in Fig. -6 may be released, when a call has not been completed, in the following manner:

When the equipment is seized, relay 20 is energized by cam 2 via the circuit: battery, lower winding of 29, RI 92, R34 and earth, through cam I. It is held vby its upper winding via TZOI, Rifi, and T45.

If the outgoing operator does not operate her calling key, then the second A. C. impulse is not received, and the relay I9 cannot be energized. After a certain lapse of time, the relay 29' is energized by cam 2 on its lower winding via T203.

t is held on its upper winding via TZDI, RIM and T45. Relay 5 is short-circuited at T292 and drops. Relay I drops, its circuit being opened at TSI. Relay 4, short-circuited by T44, RiI and RI, drops. Relays I9, i9', I8, I8', Z and 20 drop, their circuits being opened at T45.

The equipment is now free.

What is claimed is:

1. In a telephone system, a plurality of exchanges, toll trunk lines interconnecting the exchanges, subscribers lines terminating at each exchange, switches at each exchange for connecting with called subscribers thereat, toll operators positions at said exchanges, outgoing and incoming equipment and sources of alternating current of a predetermined frequency at each exchange, means at a calling and a called exchange for connecting said equipments with a trunk, means in the outgoing equipment of the calling exchange and controlled by the outgoing operator for transmitting relatively long alternating current impulses from the calling exchange to operate and to release the incoming equipment at the called exchange, and means in the incoming equipment at the called exchange for transmitting relatively short alternating current impulses to control the outgoing equipment at the calling exchange.

2, The telephone system according to claim 1 and a relay in the outgoing equipment of the calling exchange controlled by the outgoing operator for disconnecting said equipment from the incoming equipment and connecting it with a toll trunk.

3. The telephone system according to claim l, and in which the outgoing operators position comprises a calling device operable in accordance with the digits of the called number, means operable upon the connection of the incoming equipment at the called exchange with a trunk for sending a relatively short A. C. impulse over the trunk to the outgoing equipment of the calling exchange, a relay in the last-mentioned equipment responsive to said impulse for signalling the outgoing operator, a second relay in the outgoing equipment controlled by the calling device for connecting the A. C. source with the trunk for relatively long periods of time in accordance with each digit of the called number, means in the input equipment of the called exchange responsive to long A. C. impulses for operating the switches at the exchange for selecting the called line.

4. The telephone system according to claim l, means in the outgoing equipment of the calling exchange and controlled by the outgoing operator for sending relatively long A. C. impulses over a trunk, and means in the incoming equipment of the called exchange connected with said trunk and responsive to said impulses for signalling an operator at the called exchange. p

5. The telephone system according to claim 1, means in the incoming equipment at the called exchange and controlled by the called subscriber for sending relatively short A. C, impulses over the connected trunk, and relay means in the outgoing equipment at the Calling @Xchange TESpOIl- A sive to said short impulses.

6. The telephone system according to claim 1, means in the incoming equipment at the called exchange controlled by van operator at the called exchange for sending relatively short A. C. impulses over the connected trunk, and relay means in the outgoing equipment at the calling exchange responsive to said short impulses.

7. The telephone system according to claim 1, means in the incoming equipment at the called exchange responsive to the connection of said incoming equipment with a trunk for sending relatively short A. C. impulses over the connected trunk, and relay means in the outgoing equipment at the calling exchange responsive to said short impulses.

8. In a telephone system, a plurality of exchanges, toll lines interconnecting the exchanges, subscribers lines terminating at each exchange, switches at each exchange for connecting `with called subscribers thereat, toll operators positions at said exchanges, calling devices at said positions operable in accordance with the digits of the called number, outgoing and incoming equipment and sources of alternating current of a predetermined frequency at each exchange, means for connecting the outgoing equipment of the calling exchange with one end and the incoming equipment of the called exchange with the other end of a trunk, means in the outgoing equipment of the calling exchange and controlled by the outgoing operator for transmitting a relatively long alternating current impulse, means operative thereupon for connecting an impulse register with the connected incoming equipment, means controlled by the calling device of the outgoing operator for sending long A. C. impulses over the connected trunk to said register, means in the register responsive to said A. C. impulses for sending impulses to operate the switches at the called exchange for selecting the called subscriber, and means in the incoming equipment at the called exchange for transmitting relatively short alternating current impulses to. control the outgoing equipment at the calling exchange.

f CLAUDIUS F. STEWART.

GABRIEL J. M. PENET.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS `Number Name Date 1,504,228 Gooderham Aug. 12, 1924 1,859,476 Skillman May 24, 1932 1,579,236 ONeill Apr. 6, 1926 1,473,671 Davidson Nov. 13, 1923 

